Sean Eldridge, 26, is known in political circles for his advocacy of same-sex marriage and public financing of political campaigns. He and his husband, Facebook co-founder Chris Hughes, each gave $125,000 to a Super PAC that spent $250,000 boosting the state Senate candidacy of Cecilia Tkaczyk, a Duanesburg Democrat who won an open seatafter a lengthy recount. Eldridge has also raised money for Gov. Andrew Cuomo, and worked with his aides to legalize same-sex marriage in 2011 as political director for Freedom to Marry.

Eldridge filed a statement of candidacy and has hired SKDKnickerbocker, a political consulting and advertising firm. Mike Morey, a staffer with the firm, said Eldridge is “seriously considering a run for that seat.”

Gibson defeated Julian Schreibman, a Kingston lawyer, by a 53-47 margin in 2012. The 11-county 19th District covers the mid-Hudson Valley and Catskills including parts of Rensselaer and Montgomery counties.

The Canadian-born investor runs Hudson River Ventures, a firm headquartered in Kingston. Eldridge and Hughes own a house in Shokan, just west of that city in the foothills of the Catskill Mountains. It’s unclear how much time he spends there: a May, 2012 profile of Hughes and Eldridge in the New York Times was accompanied by photographs of them on an “estate” in Garrison, in Putnam County, and Eldridge’s political donations this year listed a P.O. Box and address in the area.

Eldridge declined a request for an interview, and it seems he is in the very early stages of considering his candidacy. He has not contacted the chairman of the Democratic Party in Ulster County, Frank Cardinale, though Cardinale said he has heard “rumors” Eldridge might be interested.

“I just know a little about him. He’s a pretty impressive guy,” Cardinale said. “Look: we’re looking to get as many people as possible to at least explore it. We don’t know what Julian Schreibman’s intentions are, either. We keep our options open nonetheless.”